CVE-2026-83666: Active Directory Certificate Services (AD CS) Elevation of Privilege Vulnerability

Severity: high (CVSS 7.0 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-10-13 · updated 2026-10-31
Weakness: CWE-362

Description

Concurrent execution using shared resource with improper synchronization ('race condition') in Active Directory Certificate Services (AD CS) allows an authorized attacker to elevate privileges locally.

Affected products

Microsoft Windows 10 1607: before 10.0.14393.9612 — fixed in 10.0.14393.9612
Microsoft Windows 10: before 10.0.17763.9376 — fixed in 10.0.17763.9376
Microsoft Windows Server 2012: r2 (and their updates)
Microsoft Windows Server 2016: before 10.0.14393.9612 — fixed in 10.0.14393.9612
Microsoft Windows Server 2019: before 10.0.17763.9376 — fixed in 10.0.17763.9376
Microsoft Windows Server 2022: before 10.0.20348.5761 — fixed in 10.0.20348.5761
Microsoft Windows Server 2025: before 10.0.26100.33650 — fixed in 10.0.26100.33650
Microsoft Windows 10 1607: from 10.0.14393.0 before 10.0.14393.9612 — fixed in 10.0.14393.9612
Microsoft Windows 10: from 10.0.17763.0 before 10.0.17763.9376 — fixed in 10.0.17763.9376
Microsoft Windows Server 2012: from 6.2.9200.0 before 6.2.9200.26434 — fixed in 6.2.9200.26434
Microsoft Windows Server 2012 R2: from 6.3.9600.0 before 6.3.9600.23470 — fixed in 6.3.9600.23470
Microsoft Windows Server 2016: from 10.0.14393.0 before 10.0.14393.9612 — fixed in 10.0.14393.9612
Microsoft Windows Server 2019: from 10.0.17763.0 before 10.0.17763.9376 — fixed in 10.0.17763.9376
Microsoft Windows Server 2022: from 10.0.20348.0 before 10.0.20348.5761 — fixed in 10.0.20348.5761
Microsoft Windows Server 2025: from 10.0.26100.0 before 10.0.26100.33650 — fixed in 10.0.26100.33650

How to fix

Upgrade to a fixed version: Microsoft Windows 10 1607 10.0.14393.9612; Microsoft Windows 10 10.0.17763.9376; Microsoft Windows Server 2016 10.0.14393.9612; Microsoft Windows Server 2019 10.0.17763.9376; Microsoft Windows Server 2022 10.0.20348.5761; Microsoft Windows Server 2025 10.0.26100.33650; Microsoft Windows 10 1607 10.0.14393.9612; Microsoft Windows 10 10.0.17763.9376; Microsoft Windows Server 2012 6.2.9200.26434; Microsoft Windows Server 2012 R2 6.3.9600.23470; Microsoft Windows Server 2016 10.0.14393.9612; Microsoft Windows Server 2019 10.0.17763.9376. Check the vendor advisory for mitigations.

References

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-83666

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